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Discussion Starter #1
Hi all, so I'm doing some leak down testing on my 1999 ZX9R to find the cause of low compression in one of my cylinders. This is my first time doing a leak down test, so please correct me if I am doing something wrong. Basically none of the cylinders were holding compression from a leak down test on my cold engine. When I opened the regulator on my leak down tester, I could hear and feel all the air going through my intake and exhaust valves (yes, I had the pistons at their respective TDC marks). Is this because my engine is cold? Are the clearances among all the moving parts not tight enough on a cold engine, thus causing air to escape through my valves? Here's some more information that might be helpful:
  • I have a lot of parts removed (radiator, carbs, exhaust, vacuum tubes and switches for the emissions stuff).
  • Cams are properly timed because I set it recently and haven't had the bike running yet.
  • Valves and valve guides have proper clearance. I performed wobble tests on all of them with a dial indicator and all of them were in spec.
  • Valve springs are within spec.
  • The engine has a brand new head gasket.
  • Last time I worked on the bike I checked compression, and these were my results:
    • C1: 80psi
    • C2: 90psi
    • C3: 50psi
    • C4: 90psi
Thank you in advance to anyone who might be able to point me in the right direction.
 

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You haven't got 1 low comp you've got 4 very low comp readings so much so that my first question is when did you do the comp test ?
Before or after the rebuild ? I assume from your post it was after you carried out the work ?
 

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You would set the valve lash with motor ice cold. If everything is to speck and installed right you should get good compression numbers and 8 % or less leakdown, Im curious as why it has a new head gasket? Did you install the cams & lash the valves,? have you done it before? Did you have the head or cylinder or both machined to bump up the compression? Are you running it without a base cylinder gasket?
Like several times?
That motor if stock is 11.5 : 1. those numbers are way way low. I doubt it would even run,
Im not familiar with mechanically how the valve adjustment happens,
Scratch that I just googled some pics, So its a bucket and shim type set up. Kawis are know for there hit and miss issues with the valve and seats. They can start deteriorating and the valve starts sinking down into the head and unlike a car, you start losing your valve clearance until you are at zero lash. At that point the valves are hanging open. #1. your loosing compression, #2. your losing vacuum and will have starting issues. #3. the rockers are coming in contact with the heel of the cam and the cams will start to disintegrate.
If you spin the motor around by hand to TDC of exhaust stroke can you wiggle the rocker slightly for the intake and exhaust valves? If you can tell there is clearance on the intake and exhaust side then put your leakdown tester back on and while the hole your working on has air pressure feeding into it with a brass punch get on top of the bucket 1 valve at a time and tap it with a small hammer. If thats not doable take the cams out and do the leakdown test and the brass punch deal. If its a carbon build up situation then with every tap you should see the leakage start going away.
If I was you with this problem across the board, I would just yank out the cams and do what Im saying with the leakdown test.
But Ive never witnessed a carbon build up issue causing this low of numbers. My guess is you have the cams in 1 tooth off.
I would guess you should be seeing 150 / 165 psi.
\
 

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Discussion Starter #7
You would set the valve lash with motor ice cold. If everything is to speck and installed right you should get good compression numbers and 8 % or less leakdown, Im curious as why it has a new head gasket? Did you install the cams & lash the valves,? have you done it before? Did you have the head or cylinder or both machined to bump up the compression? Are you running it without a base cylinder gasket?
Like several times?
So I installed a new head gasket because I measured my compression back before I took the engine apart, and I was getting significantly lower compression on cylinders 2 & 3 than the other two (AKA two adjacent cylinders). After the head gasket change, one of two of the cylinders jumped to the 90psi range with the others. Yes, I do have a cylinder base gasket. No, I did not get anything machined during my rebuild. I asked a question on this forum about whether or not I would need to get the head machined, and I was told that I did not need to do it because the engine doesn't warp enough for that.

As for the valve lash, I had never heard of this term until now (unless it's just a fancier word for valve clearance). I've seen the manual I'm working with talk about setting valve clearances, but I didn't think is was possible to adjust the clearance (or lash) without individual rocker arms for each valve (or each pair of valves). When you say "wiggle the rockers," are you talking about wiggling the cams, wiggling the cam lobes, or wiggling the camshaft cap? Wiggling the cap for specifically intake or exhaust valves doesn't sound possible because it's one big piece of metal. Oh and when you say "bucket" you're talking about the cam lobes right?

I would hope carbon build up isn't the issue because I lapped my valves before reinstalling them, so they were squeaky clean. There wasn't too much to begin with since the bike only has 14k miles on it. Your explanation makes sense though, so thank you for the detailed response.

I'll take a picture of my timing at the #4 TDC mark, and you guys can tell me if it's off or not. Please let me know if I should take any other pictures.
 

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Discussion Starter #8
You haven't got 1 low comp you've got 4 very low comp readings so much so that my first question is when did you do the comp test ?
Before or after the rebuild ? I assume from your post it was after you carried out the work ?
I did a compression test both before and after the rebuild. I've gotten compression in this low range before on my Ninja EX500 on a cold engine. I didn't think anything of it because, well, it's cold. My reason for the rebuild, as I said in my response right above this, is because I had much lower compression in 2 adjacent cylinders than I had in the others. I did both wet and dry tests, and the wet test didn't increase the compression by any notable amount.
 

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If a wet test raised the compression, the rings are bad. If not, the valves are leaking, either due to being bent, burnt or having insufficient clearance. The only other cause of valve leak is a collapsed seat and that's something that happens only rarely and is usually the result of blatant abuse.
 

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If a wet test raised the compression, the rings are bad. If not, the valves are leaking, either due to being bent, burnt or having insufficient clearance. The only other cause of valve leak is a collapsed seat and that's something that happens only rarely and is usually the result of blatant abuse. Your confusion concerning setting clearances points to that as the issue.
 

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lol always thought the term Valve Lash was specific to the Americas as it's referred to as "Valve clearance's" in the UK, Even in the OEM Manual, Lets be honest your checking and adjusting a clearance.
The term Lash in mind is when you tie some rouge to a pole and give him 20 lashes ;)

Reading your post I gather you didn't check/Adjust the Valve clearances at any point from the initial diagnosis to now ?
Compressions can be done hot or cold but cold gives a far better indicator.

Diagram shows fyi:-
Don't worry this is a 6R not a 9R Engine in the picture but it's all the same ref info..
Cam Lobe Red Arrow
Shim Bucket (Kawasaki call it a Tappet) shim sits underneath Green Arrow.
Clearance measured between Bucket & Cam (With Lobe opposed) Blue Arrow

Picture of you cam timing would be good but clearances need to be checked next..


 

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lol always thought the term Valve Lash was specific to the Americas as it's referred to as "Valve clearance's" in the UK, Even in the OEM Manual, Lets be honest your checking and adjusting a clearance.
The term Lash in mind is when you tie some rouge to a pole and give him 20 lashes ;)

Reading your post I gather you didn't check/Adjust the Valve clearances at any point from the initial diagnosis to now ?
Compressions can be done hot or cold but cold gives a far better indicator.

Diagram shows fyi:-
Don't worry this is a 6R not a 9R Engine in the picture but it's all the same ref info..
Cam Lobe Red Arrow
Shim Bucket (Kawasaki call it a Tappet) shim sits underneath Green Arrow.
Clearance measured between Bucket & Cam (With Lobe opposed) Blue Arrow

Picture of you cam timing would be good but clearances need to be checked next..


What's Queens English for the bucket?
 

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We call a Bucket a Bucket with ref: to the Topic in question if you orientate the shim bucket 180deg you get a Bucket that the shim sits in.
 

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Discussion Starter #14
Reading your post I gather you didn't check/Adjust the Valve clearances at any point from the initial diagnosis to now ?
No I've never checked the clearances. I'll see if I can do it tomorrow morning. I'll report back with what I find after that.

I didn't realize those little metal magnets under the buckets were the shims. Knowing that completes the puzzle of how you adjust the clearances; either swapping shims around or buying bigger/smaller ones.

Thanks for the picture and all the help so far guys. I'll let you know what I find. Cheers!
 

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That's Exactly how they are adjusted but just a side note there NOT magnetic.
Probably got that notion from the oil stiction.
No I've never checked the clearances. I'll see if I can do it tomorrow morning. I'll report back with what I find after that.

I didn't realize those little metal magnets under the buckets were the shims. Knowing that completes the puzzle of how you adjust the clearances; either swapping shims around or buying bigger/smaller ones.

Thanks for the picture and all the help so far guys. I'll let you know what I find. Cheers!
Hope you get it solved. Do you have a repair manual in hard copy or pdf? Need that.
 

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Probably got that notion from the oil stiction.
Maybe but I get the impression he has never done valve clearances before as he appears UN-familiar with the components.
Hope you get it solved. Do you have a repair manual in hard copy or pdf? Need that.
Again I have reservations that this will turn out a happy story jmho..I hope it does and +1 for a Service Manual and sit down and read before you attempt and ask if not sure before you attack the task ...
 

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Again I have reservations that this will turn out a happy story jmho..I hope it does and +1 for a Service Manual and sit down and read before you attempt and ask if not sure before you attack the task ...
Breaking into the nuts and bolts can be either a triumphant education or a demoralizing disaster.
I went by the book on my first automotive rering adventure on a 1972 Plymouth Duster and still do today.
 

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lol always thought the term Valve Lash was specific to the Americas as it's referred to as "Valve clearance's" in the UK, Even in the OEM Manual, Lets be honest your checking and adjusting a clearance.
The term Lash in mind is when you tie some rouge to a pole and give him 20 lashes ;)

Reading your post I gather you didn't check/Adjust the Valve clearances at any point from the initial diagnosis to now ?
Compressions can be done hot or cold but cold gives a far better indicator.

Diagram shows fyi:-
Don't worry this is a 6R not a 9R Engine in the picture but it's all the same ref info..
Cam Lobe Red Arrow
Shim Bucket (Kawasaki call it a Tappet) shim sits underneath Green Arrow.
Clearance measured between Bucket & Cam (With Lobe opposed) Blue Arrow

Picture of you cam timing would be good but clearances need to be checked next..


The olde English motorcycle forum I frequent has a complete English/American dictionary so the two sides of the pond can effectively communicate without (too much) confusion.

Motorcycle = Motorbike
Plug wire = HT (High Tension) lead
Rim lock = Security bolt
Wrench = Spanner
Fender = Mudguard
Triple tree = Yoke
Ground = Earth
Fork tube = Stanchion
Gear shift = Gear change
Muffler = Silencer
Gasoline = Petrol
Petcock = Petrol/Fuel tap
Wrist pin = Gudgeon pin
Zerk fitting = Grease nipple
Lifters = Tappets
Counterclockwise = Anticlockwise
Bushing/s = Bush/es
Snap ring = Circlip
Footpeg = Footrest
Transmission = Gearbox
License plate = Number plate
Kerosene = Paraffin
Axle = Spindle
Denatured alcohol = Methylated spirit (or "meths")
High beam = Main beam
Low beam = Dipped (or Dip) beam
Blinkers/Flashers/Turn signals = (Direction) Indicators
Set screw = Grub screw (as a "set screw" in the UK is a fully threaded bolt with a hexagon head)
Tube wrench = Box spanner
Box-end wrench = Ring spanner
Allen wrench = Allen key
Adjustable wrench = "Adjustable" (spanner) or "Shifter"
Vise grip = Mole grip
Breaking-in = Running-in
Flashlight = Torch
Pinging = Pinking
Hose clamp = Jubilee clip
Bondo = Body filler
Rim band = Rim tape
Headlamp bucket = Headlamp shell
Lever perch = Lever bracket
Fiberglass = GRP (Glass Reinforced Plastic)/Fibreglass
Pry = Prise
Vise = Vice
Kickstand = Side stand
Tire iron/spoon = Tyre lever
DC generator = Dynamo
Lash=Clearance_
 

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Discussion Starter #20
Hope you get it solved. Do you have a repair manual in hard copy or pdf? Need that.
I have a hard copy one. The manual for this bike is unfortunately much harder to follow than the one I had from Cyclepedia for my Ninja 500. I guess that's what you get from an original manual from 1999 huh?
 
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